A money box contains only 10-cent and 20-cent coins. There are 40 coins with a total value of $6.50. How many coins of each?
2 answers:
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Answer:
3. 2x + y = −1
Step-by-step explanation:
To find the equation of the line, we write it first in the slope-intercept form:
where
m is the slope
q is the y-intercept
From the graph, we see that the line crosses the y-axis at y = -1, so the y-intercept is -1:
Now we have to find the slope, by calculating the rate of change of the line through 2 points:
Taking the two points at (-2,3) and (1,-3), we find:
So the equation of the line is
Now we have to re-arrange it in the standard form, so in the form
where a, b and c are integer numbers.
To do that, we simply add +2x on both sides of the equation of the line in the slope-intercept form, and we get:
So, option 3).